This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present techniques. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present techniques. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
The production of hydrocarbons, such as oil and gas, has been performed for numerous years. Occasionally, oil or fuel is released onto the surface of a body of water. This is generally referred to as an “oil spill.” When such an event occurs, the oil spill is evaluated and in many cases cleaned up. The accidental release of oil or other hydrocarbons in the marine environment poses a significant threat to offshore, near-shore, and coastal areas. In many cases, immediate action may limit the extent of environmental impact.
One method of cleaning up the oil spill is by dispersing the oil into the water column below the surface to prevent the oil from washing up on shore where it may cause severe environmental damage. Liquid chemical treating agents (e.g., chemical dispersants) are generally used in such methods. Chemical dispersants are typically sprayed over the surface of an oil spill to reduce the interfacial tension between the oil and water and to allow wave action to break the oil spill into very small oil droplets. These small oil droplets disperse the oil into the water column. However, once the liquid dispersant enters the water column, it is no longer available for contacting and dispersing the oil. Hence, if the small droplets miss the oil spill, even by a small distance, they will be ineffective.
Conventional chemical dispersants have limitations that reduce their effectiveness for many real world situations. Conventional chemical dispersants tend to lose their effectiveness as the viscosity of the treated oil increases. Some oils naturally have higher viscosities than others (e.g., Bunker C). Even low viscosity crude oils weather over time into a more viscous liquid as their “light ends” dissipate. Other crude oils form emulsions with water that often have a higher viscosity than the crude oil by itself. Further, oil tends to immediately increase in viscosity upon contact with cold water. The high viscosity of the oil reduces the effectiveness of liquid dispersants by limiting the ability of the dispersant to interact with it. Many currently marketed liquid dispersants may tend to roll off or flow off the surface of the viscous oil and pass into the water column without dispersing the oil.
Another limitation of conventional dispersants is related to their delivery methods via boat or airplane. In these delivery methods, the dispersants are sprayed onto an oil spill as small 0.4 to 0.7 μm droplets because larger droplets tend to penetrate the oil spill. These small droplets, particularly when sprayed from aircraft, are expected to have significant losses due to overspray.
A related problem is that conventional chemical dispersants are clear and cannot be seen on the water or oil spill from an airplane. Thus, responders applying the dispersant may not know how well the dispersant covered the slick resulting in spraying a previously treated area or failing to treat an area. Currently these application problems are somewhat addressed by flying low (e.g. about 100 feet) over an oil spill during application.
Conventional dispersants are comprised of only 40 to 50% dispersing agent. The rest is primarily composed of solvent to increase the chances of the dispersing agent mixing with and dispersing the oil spill. The use of more solvent is good because it increases the likelihood of contact with the oil spill, but detrimental in that it limits the amount of dispersing agent, by weight, that can be used.
In addition, many conventional dispersants have a density greater than seawater. This causes droplets that penetrate or miss the slick to sink into the water column without interacting with the oil. These application problems result in overuse of dispersant, which increases costs.
One method utilized to improve dispersant effectiveness for viscous oils and emulsions involved formulating a more effective carrier solvent. Two such dispersants are COREXIT® 9500 and 9527 developed by ExxonMobil Corp. (manufactured by NALCO Chemical Co.). These dispersants are designed to be more effective because the carrier solvents remain in the oil film and resist extraction of the dispersant into the water column.
Another approach is disclosed in U.S. Pat. No. 4,560,482. This method utilizes a viscous, sticky, gel-like solvent that allows contact of the surfactants with the oil spill for a longer time interval to improve the likelihood that the oil will be dispersed into the water. However, this reference fails to teach low density, droplet size, or visibility of the viscous dispersant liquid.
U.S. Pat. No. 4,197,197 discloses an oil dispersant utilizing a water-soluble polymer and eliminating the hydrocarbon solvent from the formulation. However, this reference fails to teach low density, droplet size, or visibility of the dispersant.
Further, another approach is disclosed in PCT Patent Publication No. WO2005/115603. This reference teaches the use of solid particles including a matrix component and an effective amount of a dispersant component. The solid particles are distributed over the surface of an oil spill and the solid matrix component dissolves to release the surfactant into the oil. The matrix component is oleophilic and does not tend to roll off of viscous oils.
Microbubbles have been used in detergents for altering their density as disclosed in U.S. Pat. No. 5,176,713, but there is no teaching or suggestion to use microbubbles in a oil dispersant formulation.
Accordingly, the need exists for a more efficient dispersant that is persistent, visible when delivered during a spraying operation, is comprised of larger droplets, and tends to float on seawater. Also, a method for effectively and efficiently applying such a dispersant is needed.